July 20, 2011 -- A California company whose African dwarf frogs have been linked to at least 241 cases of salmonella illness going back to 2009 has resumed selling the tiny animals after a temporary pause.

The CDC says most of those sickened by the frog-borne bacteria have been children under the age of 5. The federal agency has warned parents that the amphibians, a type of water frog, are widely available from pet stores and online retailers.

The CDC says children under 5 are at "high risk" of serious salmonella infections and should be kept away from the creatures, their water, their habitat, and anything they touch.

The outbreak has been linked to Blue Lobster Farms in Madera County, Calif., which had stopped shipping the creatures in late April after the company's frogs had been linked to salmonella cases. But the company started sending them out again in June, according to the California Department of Public Health.

Casey Barton Behravesh, DVM, DrPH, a veterinary epidemiologist at the CDC, tells WebMD that the agency can't stop the company from selling the frogs because it is not a regulatory authority.

The company could not be reached for comment either by telephone or by email.

Barton Behravesh tells WebMD the frogs in question are about the size of a quarter and can easily spread disease by splashing water in aquariums onto items that people touch.

She says the number of reported cases is likely grossly underestimated.

"There are likely to be many more people out there than just the ones who go to the doctor," Behravesh tells WebMD. "The actual number of people in this outbreak could be substantially bigger."

Salmonella Symptoms

Salmonella infection can cause diarrhea, fever, and abdominal cramps 12 to 72 hours after exposure. In severe cases, hospitalization may be needed.

Blue Lobster Farms breeds the majority of African dwarf frogs that are sold in the U.S., the CDC says. The frogs also can be found in educational stores, pet stores, fairs, carnivals, and other venues.

Blue Lobster is listed under S & D Sales Co. of Madera, Calif., which also could not be reached for comment.

Curtis L. Fritz, DVM, PhD, the State Public Health Veterinarian for the California Department of Public Health, tells WebMD that the breeder of the frogs "has been working with local county public health and environmental health officials as well as independent laboratories and a veterinarian" from the University of California, Davis.

How Frogs Spread Salmonella

Fritz says the frog carries salmonella and other bacteria in its GI tract and does not have to come in contact with people to spread infection.

"The frogs are probably shedding salmonella into the aquarium environment in which they live and people are becoming infected by contacting the water or things in the aquarium," Fritz tells WebMD. "Our concern is not so much that the frogs are infected, we sort of expect that from the nature of them being frogs. But there is this potential for people not to be aware of the frogs' bacteria."

He says it is "perfectly legal" for the company to sell the frogs.

The California Department of Public Health put out an alert on April 26 warning that "certain pet aquatic frogs may carry bacteria that cause illness in people and should be withheld from sale to the public."

The statement says frogs from Blue Lobster Farms "are likely to be infected, have already caused multiple illnesses and hospitalizations and can contaminate tanks holding them."

Risks to Pregnant Women

The CDC says salmonella infection can cause "serious health risks" to pregnant women as well as young children, the elderly, or people with weak immune systems, including cancer patients.

CDC says salmonella infections associated with the dwarf frogs have been reported in 42 states since April 2009. Those infected range in age from less than a year old to 76.

The CDC says about 70% of patients are younger than 10, and that the median age was 5. It says 30% of patients were hospitalized but that no deaths have been reported.

The CDC says it recommends vigorous hand washing after contact with the frogs.

Fritz says parents need to know that amphibians and reptiles also can spread salmonella.